<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        *{
            margin: 0;padding: 0
        }
        .box{
            width: 100%;
            height: 500px;
            background: pink;
        }
        .box div{
            width: calc(25% - 20px);
            height: 450px;
            background: skyblue;
            float: left;
            margin: 0 10px
            /* 左右间距相同 */
        }
    </style>
</head>
<body>
    <div class="box">
        <div>1</div>
        <div>2</div>
        <div>3</div>
        <div>4</div>
    </div>
</body>
</html>
<!-- 
    calc：计算属性
        - 设置元素的宽高
        - 设置元素居中 calc-宽高的一半
        - 栅格系统 了解
 -->